As a member of the Senate Foreign Relations Committee for 30 years, Joe Biden prided himself as an expert on foreign policy. It was one of the key planks of his pitch for election as US President, after the bumpy ride under his predecessor, Donald Trump.

Unfortunately, it was never really true. Biden voted against the war to liberate Kuwait in the 1990s, in favour of the invasion of Iraq in the 2000s and he opposed the raid that killed Bin Laden (he told Barack Obama: “Don’t go”).

None of which mattered nearly as much as the chaotic American withdrawal from Afghanistan last year, which caused dismay to the US public and the country’s allies and sent a very unfortunate message to the Kremlin.

This has been compounded by the President’s tendency to make gaffes, particularly when he ventures off script – as he does all too often. He has made fun of this tendency in the past and it once mattered far less than it does now.

Running for the Democratic nomination for the presidency against Obama in 2007, for example, he awkwardly described his opponent as: “the first mainstream African-American who is articulate and bright and clean and a nice-looking guy”.

A few years later Obama observed to his staff about his then vice-president, “Never underestimate the ability of the vice-president to screw things up.”

Biden’s first gaffe during the Ukraine crisis was to suggest that Putin would face only limited sanctions if his incursion into the country was correspondingly minor.

The second was to tell members of the US 82nd Airborne Division in Poland that they would find terrible scenes there, suggesting that they might end up in Ukraine, when there was never any intention of sending them to that country.

But the mega gaffe, also in Poland, was to declare, “For God’s sake, this man [Putin] cannot remain in power.” This left the White House scrambling to say that the President hadn’t meant it, as regime change is not American policy.

Biden’s remark unfortunately is already being used by Putin and his acolytes to denounce opponents of the war in Russia as agents of the United States.

Those who know the US President will testify, as I can, that he is a nice guy, but there are worries in the US and among the Western allies as to whether that is what is required in standing up to Putin.

Biden has been clear that the alliance will defend “every inch of Nato territory”. But as leader of the free world, he has been curiously muted in responding to Putin’s threats.

It would be more encouraging to hear the US President – in a scripted question – ask Putin why he persists in threatening the Russian people with a nuclear war.

For does anyone believe that if a nuclear weapon ever were used on Nato territory, the alliance would not retaliate?

Making that red line more explicit would have more effect than calling Putin, as Biden has, a war criminal, thug and a murderous dictator, all of which is water off that particular duck’s back.

Lord Renwick is a former British ambassador to Washington, DC